The Best Corned Beef and Cabbage

Name: The Best Corned Beef and Cabbage
Ingredients: One 7-lb. corned brisket; 1 Tbsp. juniper berries; 1 Tbsp. yellow mustard seeds; 1 Tbsp. whole black peppercorns; 1 Tbsp. dried thyme; 2 tsp. whole cloves; 4 bay leaves; 1 medium garlic head, peeled; 1 medium yellow onion, halved; 12 small red potatoes (11 oz.); 6 small golden beets, peeled and trimmed (10 oz.); 6 medium carrots (12 oz.), peeled and cut into 4-inch lengths; 6 medium parsnips (11 oz.), peeled and cut into 4-inch lengths; 6 small Japanese turnips, peeled and trimmed (14 oz.); 1 small savoy cabbage (1¾ lb.), cut into 6 wedges; 1 cup Castelvetrano olives; Mustard or freshly grated horseradish, for serving